A minor, or grade 1, MCL tear can take from a few days to a week and a half to heal sufficiently for you to return to normal activities, including sports. A grade 2 tear can take from two to four weeks to heal.
A grade 3 tear usually takes from four to eight weeks to heal, unless it is associated with damage to the ACL, in which case the recovery time may be longer.

A first degree sprain is damage to only a few ligament fibres. A second degree sprain is damage to a more extensive number of ligament fibres, but the ligament remains intact.
A third degree sprain is a complete rupture of the ligament. Because of the force involved in this injury other structures in the knee, such as the Meniscus (Cartilage) or the Anterior Cruciate Ligament can also be damaged.

Sounds like he avoided any real damage so if this is true long term or reinjury should not be a concern after the initial recovery. No damage to ligament is key. Expect him to miss 12 gms and be back in early November.